Panels made of steel have generally been used as body panels of vehicles. Recently, however, Fiber Reinforced Plastic (FRP) is being used for making vehicle body panels having reduced weight.
Referring to FIGS. 1 and 2, a fiber reinforced plastic panel 10 is used as a roof panel. The fiber reinforced plastic panel 10, however, cannot be attached to a side steel vehicle body 20 by welding, such as spot welding or arc welding, and therefore must be attached by other mechanical fastening methods.
That is, the fiber reinforced plastic panel 10 and the side steel vehicle body 20 are attached to each other by forming fastening holes at the flange of the side steel vehicle body 20 and at the flange of the fiber reinforced plastic panel 10, which are supposed to be attached. The fiber reinforced plastic panel 10 is then arranged such that the flange of the panel 10 is on top of the flange of the side steel vehicle body 20. The flanges are then bonded with an adhesive 30, and then by inserting a rivet through the fastening holes, as shown in FIG. 2.
Because vehicle bodies are generally assembled by welding on current vehicle manufacturing lines, the cost for manufacturing vehicle bodies requiring other assembly methods may increase manufacturing costs. For example, when a fiber reinforced plastic panel 10 and a side steel vehicle body 20 are attached together using mechanical methods such as the method described above, additional process steps for forming the fastening holes and applying and hardening the adhesive are required. The addition of such process steps increases the cost for manufacturing vehicle bodies.
Further, the forming of a fastening hole in the fiber reinforced plastic panel 10 commonly causes delamination of the fiber reinforced plastic. In order to avoid such defects, the size of the fastening hole may need to be increased and/or the time allotted for forming the fastening hole may need to be increased.
Further, the bonding strength provided by attaching the fiber reinforced plastic panel 10 to the side steel panel 20 with bolts and nuts is small in comparison with the strength provided by spot welding of the same diameter. Therefore, more attachment points (each including a bolt and nut) are required to fasten the fiber reinforced plastic panel 10 to the side steel panel 20 with bolts and nuts, as compared to when fastening methods using welding are used.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the disclosure and therefore it may contain information that is not prior art in this country to a person of ordinary skill in the art.